1. Field of the Invention
The present invention relates, generally, to fuel injector assemblies for internal combustion engines. More specifically, the present invention relates to such a fuel injector having an improved solenoid operated check valve located below the pump chamber and above the nozzle assembly within the injector body.
2. Description of the Related Art
Fuel injector assemblies are employed in internal combustion engines for delivering a predetermined, metered mixture of fuel and air to the combustion chamber at preselected intervals. Fuel injectors commonly employed in the related art typically include a cylindrical bore formed in the main injector body. A plunger is reciprocated within the cylindrical bore to increase the pressure of the fuel. A solenoid actuated control valve is mounted in an injector side body and communicates with a source of fuel. A high pressure fuel passage extends between the solenoid actuated control valve and the cylinder bore. Fuel at relatively low pressure is supplied to the control valve which then meters the delivery of the fuel at predetermined intervals through a fuel passage to the cylindrical bore. Fuel at very high pressures is delivered to a fuel nozzle assembly and ultimately dispersed from the injector.
In the case of compression ignition or diesel engines, the fuel/air mixture is delivered at relatively high pressures. Presently, conventional injectors are delivering this mixture at pressures as high as 32,000 psi. These are fairly high pressures and have required considerable engineering attention to ensure the structural integrity of the injector, good sealing properties and the effective atomization of the fuel within the combustion chamber. In essence, the modern diesel engine must provide substantial fuel economy advantages while meeting ever more stringent emission regulations. However, increasing demands for greater fuel economy, cleaner burning, fewer emissions and NO.sub.x control have placed, and will continue to place, even higher demands on the engine's fuel delivery system, including increasing the fuel pressure within the injector.
In part to meet the challenges discussed above, electronic engine control modules have been employed to control the beginning and end of the fuel injection event, injection timing and fuel quantity, to improve fuel economy and meet emission requirements.
However, problems still remain. For example, fuel injectors of the type commonly known in the art and briefly described above often include relatively long, internal fuel flow passages. These passages include those extending from the control valve to the pump chamber, passages extending from the pump chamber to the nozzle assembly and passages extending between the high pressure fuel passage and any low pressure fuel return passages. During an injection event, it is not uncommon for pressure waves to develop within these passages. The dynamics of such pressure waves can have a negative effect on fuel injection. In addition, injectors which include shared passages for both fuel feed in and spilling are particularly susceptible to this problem.
Furthermore, it is not uncommon for the solenoid actuated control valve used in the injectors of the related art to experience mechanical bouncing as the valve member is cycled between its open and closed positions. This causes imprecise injection control at the beginning and end of the injection event and is undesirable. Thus, there is an ongoing need in the art for better control over these injection parameters during the span of the injection event in a cost effective manner.